Electro-optic modulators change refractive index of a branch of a waveguide (hereinafter the modulated branch) by an electro-optic effect of a modulating electric field. Thus, the electro-optic modulator can alter a phase of light waves traversing the modulated branch. As a result, a phase shift is generated between the light waves traversing the modulated branch and light waves traversing another branch of the waveguide (hereinafter the non-modulated branch). The light waves traversing the modulated branch interface with light waves traversing the non-modulated branch. Output energy of the light waves of the waveguide is modulated as the output energy depends on the phase shift, which in turn depends on the modulating electric field. The light waves have transverse electric wave (hereinafter the TE mode) and transverse magnetic waves (hereinafter the TM mode). A modulating efficiency of the electro-optic modulator is determined by modulating the TE mode and the TM mode.